In general, body implants such as dental screws are surgically inserted in the bones of a patient, such in the jaw, wherein the implant is integrated to the bone. In the field of dentistry, implants to be screwed or pressed inside a cavity perforated in the bone are well known.
Actually, one of the greatest challenges in piezoelectric surgery is based on correctly expanding the bone tables in important defects and knife edges in order to allow the correct location of an implant, to maintain the architecture and the bone function thereby guaranteeing the functional and aesthetic rehabilitation.
Unfortunately, up to date the traditional techniques disclosed in the literature just refer to the sandwich technique which was initiated by maxillofacial surgeons more than 20 years ago by using saws for the separation of bone tables which generally originates a great loss of bone tissue in the zone where the implant is done. Other techniques have tried to use the insertion of internal and external auto-grafts (known in the technical field as on-lay and in-lay), which besides of being complex, is traumatic and the results basically depend on the skill, preparation and expertise of the surgeon. However, many of the problems related with bone insufficiency can be solved through more conservative techniques.
From year 2000, when Tommaso Verselloti dabbled with the concept of piezo-surgery in the field of dentistry using inserts which allow to make fine cuts in narrower bone tables, the technique known as sandwich technique took great relevance again. Such technique requires of some vestibular bone relaxants which allow to expand the tissue for the location of the bone graft and thus guaranteeing the stability thereof with optimal quality. However, the immediate location of implants in bone cortical less than 2 mm of calibration in the peak area is counterproductive due to the fact that four problems are generated:                Wrong positioning of the implants,        Secondary slope of the implants,        Fracture of the weakest cortical area in the maxillary vestibular and in the maxillary lingual; and        Reabsorption of the bone cortical area with the consequent exposure of implant threads and aesthetic defects due to such exposure.        
Although with the prior technique it was possible to successfully expand the bone tables, depending on the type of defect, common implants do not stay in the optimal position for an aesthetic rehabilitation requiring thereby known castable abutments (widely known as “UCLA” type abutments) for correcting wrong positions, and even in extreme cases it is necessary to remove the implant. These results were mainly caused by not understanding the ways of trabecular bone to make the internal bone cuts whether they are vertical, horizontal and oblique.
In addition, in many cases it can be seen that during the expansion and further location of the implants in the correct position, after one month such implants are in different positions to the original ones, mainly distally and mesially, which is mainly caused by the vestibular relaxants made to achieve the expansion of the bone tables. These implant movements are commonly known as secondary tilt and have been associated with the non-controlled bone expansion.
In addition to the above, the implants found in the state of the art also represented the problem of the cortical fracture, due to the pressure generated by the implant in the peak area caused by the cylindrical design used before the present invention. Such design generates a loss of continuity of the bone tissue vertically with some variations during the placing of the implant in the final stage, i.e. when the closing laps of the thread are being introduced.
Likewise, the absorption of the bone cortical area generated by the loss of bone tissue vertically has been disclosed, which is caused by the pressure generated by the expanders. The only solution detected for such problem is to make bone integration, but the aesthetic results produced were undesirable.
Accordingly, one of the greatest challenges is to make the bone expansion and to avoid such inconvenient. In order to improve the achievements done with the cylindrical implants the screws for implants of the present invention have been developed characterized in that its body is a threaded cylinder and one of its ends is tapered for facilitating the introduction of the screw in the bone. One of such type of screws can be found in the industrial design U.S. D603,513, which discloses a screw being formed by a cylindrical body covered by a thread system wherein the gap between threads is the same, a threaded and tapered end and a flat upper area having inside a tapered seat and an hexagonal space, in which the attachment or inner abutment and notches located parallel to the longitudinal axis of the screw in the lower part thereof are adjusted.
There has also been an effort in improving the shape of the threads located on the screws and as disclosed in application U.S. 2008/0241791, which discloses a dental implant having a body with blunt threads and other sharp edges in order to help forming a thread inside the bone to the perforated.
Similarly, document U.S. Pat. No. 7,240,542 discloses implants showing cylindrical screws with an apical and a coronal end. Such screw is slanted in the upper or coronal part in a determined angle in order that the implant accommodates to the jaw bone anatomy of the patient. The implant in its longitudinal configuration is funnel shaped wherein the diameter decreases from the upper part to become smaller in the lower part. In addition, this design shows that the upper part has a thread with gaps, between each thread, less than the space between the threads in the lower part.
On the other hand, patent EP 1416872 teaches a screw to be inserted in the bone wherein the upper part of the screw shows a thread with a gap smaller than the space for the thread in the lower part thereof. In addition, such patent shows that the coronal part (upper part of the implant) has an axial length such that when the implant is installed, the configuration of such portion is confined with the bone cortical tissue layer of the patient, due to a tapered configuration of no more than 5° with respect to the external surface of the lower part of the screw.
U.S. Pat. No. 5,527,183 discloses an orthopedic implant having a coronal end, a distal end and a plurality of segments, namely four in the upper part of the implant and the lower part having a finer thread, i.e. with a smaller gap compared to the one showed for the four segments in the upper part.
Actually the closest document in the state of the art to the present invention is formed by a screw commercially available under the trademark Nobelactive from Nobelbiocare, which is characterized by having a tapered and threaded body and an inverted cone shaped coronal region, which length does exceed 10% of the total length of the screw and according to the manufacturer, it is useful for increasing the alveolar bone volume around the implant. Despite having the above indicated feature, such implants do not avoid the fractures of the bone crest, the tilts of the implant and the bone reabsorption of bony ridges less than 3 mm.
In view of the above cited information it is clear that there was a need in the state of art which had not been fulfilled for providing a screw which avoids the inconvenient associated to the secondary tilt, fracture of the bone cortical and its reabsorption, achieving a greater irrigation of the bone tissues.
The inventor surprisingly found that the reduction of the upper and lower ends of the screw, specially so the upper cone has a length between 20% and 80% of the total length of the screw, creating a double cone which allows to reduce the pressure exerted by the traditional implant on the bone releases tensions, minimizing thereby the risk of vertical fractures and avoiding the process of bone reabsorption and therefore, avoiding problems usually related with implantation processes, such as periimplantitis and loss of support tissue, with the subsequent loss of implant.
In addition to the above, with the novel double tapered shape of the screw for implant disclosed herein, the screw exerts less pressure on the expanded bone tissue, does not generate secondary tilt, allows an excellent apical fixation guaranteeing bone integration and producing less trauma on the patient minimizing thereby pain and inflammation produced by the expansion of the bone. Likewise, the extra-oral implants with double cone could be used for rehabilitation with better prognosis and better durability in the patient than cylindrical implants.